The SMS authentication
module allows to authenticate users via SMS. There are two authentication
methods sms and password_sms which can be used in the authentications
list of the session section in the configuration.

The sms method just send a code via SMS to the user. Then the user needs to
transcribe the code into the login dialog.

The password_sms method send a code only after the user entered a valid
password. This provides a two-factor authentication method.

Both methods require that the user has a Mobile phone number defined
otherwise he can not be authenticated with those methods.